Vehicle and other seats commonly include a recliner mechanism to adjust the position of the seat back relative to the seat base. Such manual recliner mechanisms often include a lever handle located on a side of the vehicle seat for actuation of the recline feature by the occupant. When the occupant desires to change the position of the seat back, he or she actuates the lever, unlocking the seat back typically against the force of a spring biasing the seat back in a given direction, most commonly in the forward direction. With the recliner mechanism released, the occupant is free to alter the position of the seat back relative to the seat base. The position of the seat back is locked into position when the lever is released or located back in its original or locked position.
Because such seat recliner mechanisms are common in the highly competitive automobile industry, it is increasingly important to produce as inexpensive a recliner mechanism as possible while maintaining a robust recliner mechanism. It is necessary to insure that the recliner mechanism is sufficiently robust so the seat back does not alter its position on an unwanted occasion, exhibits proper characteristics in high load conditions and has an appropriate useful life. Furthermore, due to the limited space inside the passenger compartment of automobiles, it is increasingly important to provide a recliner mechanism that accomplishes the above while using a minimum amount of space and at a lower cost.
In many conventional recliner mechanisms one of the above objectives must often be compromised to satisfy the other objectives. For example, a number of highly robust recliner mechanisms will include several components that are made from costly high strength materials. Other mechanisms use highly complex arrangements of components resulting in greater size, complexity and cost. An increased number of parts or the use of high-strength materials, however, also often result in a higher cost to manufacture and assemble. If lower cost, less durable components are used, however, the overall strength of the recliner mechanism will be negatively affected, resulting in lower customer satisfaction and quality.
It is known to use a round sector mechanism in a recliner mechanism for use in a vehicle seat. For example, see U.S. Pat. No. 5,935,698 which discloses the use of a round sector gear in a recliner mechanism. Further, it is known to use pawl members in combination with a curved sector gear. It is also known that round recliners can be used to adjust the seat back with respect to the seat base and lock the seat back in place. Numerous examples of such round recliner mechanisms exist in the prior art. For example, see U.S. Pat. No. 4,995,669, to Croft; U.S. Pat. No. 5,590,931, to Fourrey et al.; U.S. Pat. No. 5,558,402 to Yamada; U.S. Pat. No. 4,408,799, to Bowman; U.S. Pat. No. 5,685,440 to Minai; U.S. Pat. No. 5,524,970, to Kienke et al.; U.S. Pat. No. 6,149,235, to Fahim; U.S. Pat. No. 6,120,098, to Magyar et al.; and U.S. Pat. No. 6,305,748 to Ohba. However, while the above prior art patents disclose numerous mechanisms for moving the pawl members into and out of engagement with the sector member, none do so in a highly simple and efficient manner while providing a sufficiently strong recliner mechanism that will perform adequately in the varied conditions of an automotive seat.
In particular, the prior art discloses and teaches that the round sector member having ring gear teeth located on an inner side of the ring gear and pawls are co-located inside of the ring sector gear and aligned to engage the teeth of the ring gear. Additionally, several of the above patents disclose the use of a plurality of translating or pivoting pawl members operated using a cam mechanism to activate and move the pawls out of engagement with a sector member. Due to the compact size limitations for vehicle seat recliner mechanisms and the high loads incurred, it is known to use multiple pawl members, even four or six pawl members, to distribute the loads around the sector gear. However, with the increased number of pawl members, the complexity associated with operating the pawl members and maintaining proper operating conditions of the recliner mechanism increases as well as the total weight of the recliner mechanism. Further, while it is known to move the pawl members with respect to the round sector gear using various known mechanisms such as cams to translate, rotate or otherwise move the pawl member with respect to the round sector gear, such mechanisms have proven inadequate since there remains an insufficient amount of contact between the pawl member and the round sector gear to carry and distribute the substantial loads in the recliner mechanism.
Accordingly, there remains a significant need to develop a round sector gear recliner mechanism capable of carrying the loads necessary to function as a recliner mechanism in a vehicle seat that can be packaged within the space requirements at a sufficiently low cost and overcomes the drawbacks of the prior art.